Filled polyketone blend
FIELD OF THE INVENTION 
     This invention relates to polyketone polymers, and, more particularly, to a filled polymer compound comprising a major portion of a polyketone polymer and lesser portions of calcium hydroxyapatite on a volume basis. 
     BACKGROUND OF THE INVENTION 
     The class of polymers of carbon monoxide and olefins has been known for some time. U.S. Pat. No. 2,495,286 (Brubaker) discloses such polymers of relatively low carbon monoxide content in the presence of free radical initiators, e.g., peroxy compounds. G.B. No. 1,081,304 discloses similar polymers of higher carbon monoxide content in the presence of alkylphosphine complexes of palladium compounds as catalyst. U.S. Pat. No. 3,694,412 (Nozaki) extended the reaction to produce linear alternating polymers in the presence of arylphosphine complexes of palladium moieties and certain inert solvents. 
     More recently, the class of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon, now becoming known as polyketones or polyketone polymers, has become of greater interest. U.S. Pat. No. 4,880,903 (VanBroekhoven et al.) discloses a linear alternating polyketone terpolymer of carbon monoxide, ethylene, and other olefinically unsaturated hydrocarbons, such as propylene. Processes for production of the polyketone polymers typically involve the use of a catalyst composition formed from a compound of a Group VIII metal selected from palladium, cobalt or nickel, the anion of a strong non-hydrohalogenic acid and a bidentate ligand of phosphorus, arsenic or antimony. U.S. Pat. No. 4,843,144 (VanBroekhoven et al.) discloses a process for preparing polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon using the preferred catalyst comprising a compound of palladium, the anion of a non-hydrohalogenic acid having a pKa of below about 6 and a bidentate ligand of phosphorus. 
     The resulting polymers are relatively high molecular weight materials having established utility as premium thermoplastics in the production of shaped articles, such as containers for food and drink and parts for the automotive industry, which are produced by processing the polyketone polymer according to well known methods. For some particular applications it is desirable to have properties which are somewhat different from those of the polyketone polymers. The more desirable properties of the polyketone polymers may be retained, and yet other properties improved, through the provision of a filled polymer compound. Reinforcing a polymer with a filler often provides a less expensive product, in addition to desirable properties for various applications. 
     Mineral-filled polyketone compounds with certain desirable properties are disclosed in U.S. Pat. No. 4,851,470 (George). The neat polyketone polymer has an unfortunate tendency to form chemical crosslinks at melt processing temperatures, as evidenced by a steady increase in melt viscosity as the polymer is processed. Mineral fillers frequently possess a variety of ionic species which are capable of intensifying melt processing problems for the polyketone polymer, such as accelerating crosslinking of the polymer, thereby limiting the melt processability of the filled polyketone compounds. 
     It is an objective of this invention to provide a filled polyketone polymer compound that exhibits little or no viscosity increase during melt processing. The filled polyketone polymer compounds of the subject invention exhibit viscosity levels during processing that are unexpectedly lower than the viscosity levels typical for compounds filled with commonly used commercial fillers, and yet exhibit mechanical properties at least equal to those of compounds filled with such commercial fillers. 
     SUMMARY OF THE INVENTION 
     The present invention provides certain filled polymer compounds of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon, filled with one or more hydroxyapatites of the formula M 10  (PO 4 ) 6  (OH) 2 , where M is barium (Ba), strontium (Sr), or calcium (Ca). More particularly, the invention provides filled compounds comprising the linear alternating polymer having calcium hydroxyapatite incorporated therein. The invention also includes articles of manufacture prepared from, and coated with, such filled compounds. 
     DESCRIPTION OF THE INVENTION 
     The polyketone polymers which are employed as the major component of the filled polymer compounds of the invention are of a linear alternating structure and contain substantially one molecule of carbon monoxide for each molecule of unsaturated hydrocarbon. Suitable ethylenically unsaturated hydrocarbons for use as precursors of the polyketone polymers have up to 20 carbon atoms inclusive, preferably up to 10 carbon atoms, and are aliphatic such as ethylene and other α-olefins including propylene, 1-butene, isobutylene, 1-hexene, 1-octene and 1-dodecene, or are arylaliphatic containing an aryl substituent on an otherwise aliphatic molecule, particularly an aryl substituent on a carbon atom of the ethylenic unsaturation. Illustrative of this latter class of ethylenically unsaturated hydrocarbons are styrene, p-methylstyrene, p-ethylstyrene and m-isopropylstyrene. The preferred polyketone polymers are copolymers of carbon monoxide and ethylene or terpolymers of carbon monoxide, ethylene and a second ethylenically unsaturated hydrocarbon of at least 3 carbon atoms, particularly an α-olefin such as propylene. 
     When the preferred polyketone terpolymers are employed as the major polymeric component of the blends of the invention, there will be within the terpolymer at least about 2 units incorporating a moiety of ethylene for each unit incorporating a moiety of the second hydrocarbon. Preferably, there will be from about 10 units to about 100 units incorporating a moiety of the second hydrocarbon. The polymer chain of the preferred polyketone polymers is therefore represented by the repeating formula 
     
         --CO--CH.sub.2 --CH.sub.2)].sub.x [CO--G)].sub.y 
    
     wherein G is the moiety of ethylenically unsaturated hydrocarbon of at least 3 carbon atoms polymerized through the ethylenic unsaturation and the ratio of y:x is no more than about 0.5. When copolymers of carbon monoxide and ethylene are employed in the blends of the invention, there will be no second hydrocarbon present and the copolymers are represented by the above formula wherein y is zero. When y is other than zero, i.e., terpolymers are employed, the --CO--CH 2  CH 2  -- units and the --CO--G-- units are found randomly throughout the polymer chain, and preferred ratios of y:x are from about 0.01 to about 0.1. The end groups or &#34;caps&#34; of the polymer chain will depend upon what materials were present during the production of the polymer and whether or how the polymer was purified. The precise nature of the end groups does not appear to influence the properties of the polymer to any considerable extent so that the polymers are fairly represented by the formula for the polymer chain as depicted above. 
     Of particular interest are the polyketone polymers of number average molecular weight from about 1000 to about 200,000, particularly those of number average molecular weight from about 20,000 to about 90,000 as determined by gel permeation chromatography. The physical properties of the polymer will depend in part upon the molecular weight, whether the polymer is a copolymer or a terpolymer and, in the case of terpolymers, the nature of the proportion of the second hydrocarbon present. Typical melting points for the polymers are from about 175° C. to about 300° C., more typically from about 210° C. to about 270° C. The polymers have a limiting viscosity number (LVN), measured in m-cresol at 60° C. in a standard capillary viscosity measuring device, from about 0.5 dl/g to about 10 dl/g, more frequently from about 0.8 dl/g to about 4 dl/g. 
     A preferred method for the production of the polyketone polymers is illustrated by U.S. Pat. No. 4,843,144 (Van Broekhoven et al.). The carbon monoxide and hydrocarbon monomer(s) are contacted under polymerization conditions in the presence of a catalyst composition formed from a compound of palladium, the anion of a non-hydrohalogenic acid having a pKa (measured in water at 18° C.) of below about 6, preferably below 2, and a bidentate ligand of phosphorus. The scope of the polymerization is extensive but, without wishing to be limited, a preferred palladium compound is a palladium carboxylate, particularly palladium acetate, a preferred anion is the anion of trifluoroacetic acid or p-toluenesulfonic acid and a preferred bidentate ligand of phosphorus is 1,3-bis(diphenylphosphino)propane or 1,3-bis[di(2-methoxyphenyl)phosphino]propane. 
     The polymerization to produce the polyketone polymer is conducted in an inert reaction diluent, preferably an alkanolic diluent, and methanol is preferred. The reactants, catalyst composition and reaction diluent are contacted by conventional methods such as shaking, stirring or refluxing in a suitable reaction vessel. Typical polymerization conditions include a reaction temperature from about 20° C. to about 150° C., preferably from about 50° C. to about 135° C. The reaction pressure is suitably from about 1 atmosphere to about 200 atmospheres but pressures from about 10 atmospheres to about 100 atmospheres are preferred. Subsequent to polymerization, the reaction is terminated as by cooling the reactor and contents and releasing the pressure. The polyketone polymer is typically obtained as a product substantially insoluble in the reaction diluent and the product is recovered by conventional methods such as filtration or decantation. The polyketone polymer is used as recovered or the polymer is purified as by contact with a solvent or extraction agent which is selective for catalyst residues. 
     The second component of the filled polymer compounds of the invention comprises a hydroxyapatite of the formula M 10  (PO 4 ) 6  (OH) 2 , where M is barium (Ba), strontium (Sr), or calcium (Ca). The preferred hydroxyapatite is calcium hydroxyapatite, Ca 10  (PO 4 ) 6  (OH) 2 , a naturally occurring calcium phosphate and the major constituent of bone and tooth mineral. It is a finely divided, crystalline, non-stoichiometric material rich in surface ions which are readily replaced by fluoride ions. Calcium hydroxyapatite is also referred to as tribasic calcium phosphate. 
     The filled polymer compounds of the invention comprise a major amount, on a volume basis, of the linear alternating polymer of carbon monoxide and at least one ethylenically unsaturated hydrocarbon with lesser amounts of a hydroxyapatite filler. The amount of hydroxyapatite present in the filled compounds of the invention is not critical, as long as other important polymer properties for the intended use are not adversely affected. Amounts of hydroxyapatite present in the filled compounds, on a volume basis, may be from about 15 vol % to about 45 vol %, based on total composition, with amounts from about 5 vol % to about 30 vol % hydroxyapatite preferred. On a weight basis, the amount of hydroxyapatite present may be greater than 50 wt %, due to its greater density. Amounts of hydroxyapatite present in the filled compounds, on a weight basis, may be from about 10 wt % to about 70 wt % or more hydroxyapatite, based on total composition, with amounts from about 30 wt % to about 50 wt % hydroxyapatite being preferred for a wide variety of uses. 
     The method of producing the filled polymer compounds of the invention is not material so long as a relatively uniform distribution of the hydroxyapatite filler throughout the polyketone is obtained. The hydroxyapatite filler exists as a discrete phase in the polyketone matrix. The method of producing the compounds is that which is conventional for polymeric fillers. In one modification, the hydroxyapatite filler and polyketone are mixed and passed through an extruder operating at high RPM to produce the filled compound as an extrudate. In an alternate modification, the components are blended in a mixing device which exhibits high shear. 
     The filled polymer compounds of the invention may also include other additives such as antioxidants, dyes, other fillers or reinforcing agents, fire resistant materials, mold release agents, colorants and other materials designed to improve the processability of the polymers or the properties of the resulting compound. Such additives are added prior to, together with, or subsequent to the blending of the polyketone and hydroxyapatite. The presence of these additives may affect the optimum level of hydroxyapatite for a given application. 
     The compounds are processed by methods such as extrusion and injection molding into sheets, films, plates and shaped parts. The compositions of the invention are particularly useful for the production of articles by multiple melting/crystallization cycles, and where elevated temperatures are likely to be encountered. Illustrative of such applications are the production of articles useful in both rigid and flexible packaging applications, and in both internal and external parts for automotive use. 
     While not wishing to be bound by any particular theory, it is believed that the advantageous results of the invention are obtained because the hydroxyapatite has ion exchange and acid scavenging properties that allow it to neutralize the effect of ionic or acidic species that accelerate a viscosity increase in the polyketone polymer in the melt state. Since few polymers exhibit such a tendency towards viscosity increase, the use of hydroxyapatite as a filler for the polyketone polymer is particularly advantageous, providing filled compounds that are readily processable into materials which exhibit useful mechanical properties. 
     The invention is further illustrated by the following Examples which should not be regarded as limiting. 
    
    
     EXAMPLE 1 
     A linear alternating terpolymer of carbon monoxide, ethylene, and propylene (89/056) was produced in the presence of a catalyst composition formed from palladium acetate, trifluoroacetic acid and 1,3-bis[di(2-methoxyphenyl)phosphino]propane. The polyketone polymer had a melting point of about 223° C. and an LVN of about 1.1 dl/g when measured in m-cresol at 60° C. The polyketone polymer also contained 0.5% Ethanox 330 and 0.5% Nucrel 535. 
     EXAMPLE 2 
     Filled compounds were prepared of the polymer of Example 1 and three different fillers: calcium hydroxyapatite, calcium carbonate, and mica. The blends prepared are shown in Table 1. 
     The blends were compounded in a 30 mm Haake co-rotating twin screw extruder, operating at 100 rpm with a melt temperature of 250° C. The viscosity of each sample was determined over time in the melt in a Rheometrics parallel plate rheometer operating at 275° C. at a frequency of 1 HZ. Table 1 lists the initial melt viscosity and the viscosity after both 10 and 28 minutes, as well as a ratio of the melt viscosity after 28 minutes to the initial melt viscosity. 
     
                                           TABLE 1                                 
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            Polyketone                                                    
                    Filler  Viscosity (Pa-sec)                            
                                        Viscosity                         
Filler      wt % (vol %)                                                  
                    wt % (vol %)                                          
                            0 min                                         
                                10 min                                    
                                    28 min                                
                                        Ratio                             
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None        100 (100)                                                     
                    0 (0)   63  113 1030                                  
                                        16                                
Calcium Hydroxyapatite                                                    
            77 (90) 23 (10) 225 380 1080                                  
                                        4.8                               
Calcium Hydroxyapatite                                                    
            60 (80) 40 (20) 1230                                          
                                2450                                      
                                    8960                                  
                                        7.3                               
Calcium Carbonate                                                         
            64 (80) 36 (20) 500 1200                                      
                                    73,410                                
                                        147                               
Mica        62 (80) 38 (20) 2250                                          
                                7510                                      
                                    52,630                                
                                        23                                
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     The addition of a solid filler to the polyketone polymer inherently results in a viscosity increase in the melt state for the filled compound. Thus, the ratio of melt viscosity after 28 minutes to the initial melt viscosity provides a relative measure of the viscosity increase that occurs when various fillers are added to the polyketone polymer. 
     The compounds filled with calcium hydroxyapatite demonstrated superior melt stability, based on these rheometric data, relative to the other filled compounds. Only the calcium hydroxyapatite filled compounds gave a viscosity ratio which was less than that of the neat polyketone polymer, indicating stabilization. The viscosity ratios for the compounds filled with calcium carbonate and mica (both commercial fillers) were significantly higher, indicating destabilization in the melt state. 
     EXAMPLE 3 
     Subsequent to blending, specimens of the blends of Example 2 were molded into plaques on a 25 ton Arburg injection molding machine. Molded specimens were stored over desicant until testing. Mechanical testing was performed on &#34;dry as molded&#34; specimens. Results of mechanical testing are shown in Table 2. 
     The mechanical property data indicate that calcium hydroxyapatite is an acceptable filler for the polyketone polymer, and provides filled compounds with properties which are comparable to those made with common commercial fillers, such as calcium carbonate and mica. 
     Other embodiments of the invention will be apparent to those skilled in the art from a consideration of this specification, or by practice of the invention described herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims. 
     
                                           TABLE 2                                 
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                          Flexural                                        
                               Flexural                                   
                                    Tensile    Impact Properties          
          Polyketone                                                      
                  Filler  Modulus                                         
                               Strength                                   
                                    Strength                              
                                         Elongation                       
                                               Izod Gardner               
Filler    wt % (vol %)                                                    
                  wt % (vol %)                                            
                          (kpsi)                                          
                               (psi)                                      
                                    (psi)                                 
                                         (%)   (ft-lb/in)                 
                                                    (in-lbs)              
__________________________________________________________________________
None      100 (100)                                                       
                  0 (0)   259   9,260                                     
                                    9,130                                 
                                         86    1.93 126                   
Calcium Hydroxy-                                                          
          77 (90) 23 (10) 323   9,980                                     
                                    7,610                                 
                                         14    1.31 6                     
apatite                                                                   
Calcium Hydroxy-                                                          
          60 (80) 40 (20) 568  12,371                                     
                                    7,280                                 
                                         5.1   0.59 3                     
apatite                                                                   
Calcium Carbonate                                                         
          80 (90) 20 (10) 318   9,820                                     
                                    7,820                                 
                                         27    1.03 41                    
Calcium Carbonate                                                         
          64 (80) 36 (20) 402  10,150                                     
                                    6,680                                 
                                         17    0.72 19                    
Mica      78 (90) 22 (10) 533  12,920                                     
                                    8,870                                 
                                         11    0.92 8                     
Mica      62 (80) 38 (20) 849  13,310                                     
                                    9,140                                 
                                         3.5   0.61 5                     
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